The present invention relates generally to a mechanical, adjustable seat suspension device and, more specifically, to a cable drive mechanical seat suspension device which uses springs and a cable to allow a seat occupant to conveniently adjust the vertical position of a seat and which allows for a substantially linear force-versus-deflection curve, and which allows height adjustment to a plurality of vertical positions.
There is a continuing need for suspension mechanisms that are simply constructed and inexpensive while still meeting vehicle manufacturers' ever increasing demands for compactness and comfort. An additional need exists for such a device whose suspension and ride characteristics can be easily modified. Other difficulties have been encountered in the height adjustment mechanisms of seat suspensions. Frequently, such mechanisms are difficult to reach, require levers or triggers that can pinch an operator, and generally are complicated and expensive.
Most known seat suspensions transmit the load from the seat to the suspension springs through steel bars comprising scissor arms or parallelogram linkages. Typical of these prior art devices include the following: U.S. Pat. No. 3,339,906 to Persson; U.S. Pat. No. 3,826,457 to Huot de Longcham; and U.S. Pat. No. 4,125,242 to Meiller et al. In such systems, the forces exerted on the suspension system by the seat occupant may be carried by a cam and a roller bearing. An example of such a system is described in U.S. Pat. No. 5,125,631 to Brodersen et al. and U.S. Pat. No. 4,448,386 to Moorhouse et al. Such systems are efficient and advantageous in that they allow substantial vertical seat adjustment and suspension. A disadvantage with such systems is that a substantial force is exerted on an arcuate cam and a roller bearing and often in a single-point contact relationship. This force requires hardened metal surfaces and durable components which can be expensive. Point-to-point surface contact also increases the difficulty of achieving a dependable, consistent linear relationship between suspension force and vertical deflection due to "noise" between contacting surfaces. It would thus be highly desirable for a seat suspension to provide maximum height adjustment and compactness while also being economical and providing a desired force-deflection linear relationship. It would be similarly desirable to provide such a seat suspension which provides height adjustment capabilities to discreet positions while allowing suspension and ride zone adjustment at each position.